1. Field of the Invention
The present invention relates to a fuel swirl generation type fuel injection valve and a direct fuel injection type spark ignition internal combustion engine mounted with the fuel injection valve.
2. Description of the Related Art
Direct fuel injection type spark ignition internal combustion engines mounted with a fuel injection valve having a plurality of fuel injection holes are known, for example, in Japanese Patent Publications SHO No. 62-48916, SHO No. 62-121827 and SHO No. 61-167116; and Japanese Utility Model Publications SHO No. 62-87169 and SHO No. 62-87127, though those fuel injection valves are not fuel swirl generation types. Fuel swirl generation type fuel injection valves are known, for example, in Japanese Utility Model Publication SHO No. 58-29162, though it does not disclose how such a fuel injection valve is applied to a direct fuel injection type engine. Although Japanese Utility Model Publication SHO No. 61-171869 discloses a needle valve having grooves for generating fuel turbulence by causing the fuel flow flowing through the grooves to collide with a straight fuel flow, it can not be classified in a fuel swirl generation type.
In some of the direct fuel injection type engines, for example, in the engine of Japanese Patent Publication SHO No. 62-48916, the fuel injection valve is located close to the spark plug and has a main fuel injection hole and a subsidiary fuel injection hole. The main fuel injection hole injects fuel in the same direction as that of the intake gas swirl, and the subsidiary fuel injection hole injects fuel in a direction toward a portion of a wall surface of the combustion chamber located upstream of the spark plug in the intake gas swirl flow direction. Smooth ignition is obtained because the fuel injected through the subsidiary fuel injection hole and adhering to the combustion chamber wall surface is evaporated at the surface, the evaporation being assisted by the intake gas swirl and the fuel being conveyed by the swirl to the spark plug in a rich condition. On the other hand, because the fuel injected through the main fuel injection hole is scattered in the combustion chamber by the swirl, a combustion effectively using the air, that is, a combustion with a high air use rate is obtained. As will be understood from the above, the intake gas swirl is inevitable for promotion of fuel evaporation.
However, there exist some problems in the intake gas swirl assist engine. Namely, in the case where the swirl is weak, scattering of the fuel injected through the main fuel injection hole will be insufficient and it is difficult to obtain good combustion with a high air use rate. On the contrary, in the case where the swirl is strong, it is difficult to obtain good ignition, because the fuel evaporated at the combustion chamber wall surface and conveyed to the spark plug is excessively blown out by the strong swirl. In this instance, because a strength of the swirl changes corresponding to the intake gas amount and the engine speeds, it is very difficult to obtain both good ignition and good combustion over the entire engine operation range.